Bioaerosol characterization represents a major challenge for the risk assessment and management of exposed people. One of the most important bioaerosol sources is the organic waste collection and treatment. This work analyzed and discussed the literature with the purpose of investigating the main techniques used nowadays for bioaerosol monitoring during organic waste treatment. The discussion includes an overview on the most efficient sampling, DNA extraction, and analysis methods, including both the cultural and the bio-molecular approach. Generally, an exhaustive biological risk assessment is not applied due to the organic waste heterogeneity, treatment complexity, and unknown aerosolized emission rate. However, the application of bio-molecular methods allows a better bioaerosol characterization, and it is desirable to be associated with standardized cultural methods. Risk assessment for organic waste workers generally includes the evaluation of the potential exposition to pathogens and opportunistic pathogens or to other microorganisms as biomarkers. In most cases, Saccharopolyspora rectivirgula, Legionella spp., Aspergillus spp., and Mycobacterium spp. are included. Future perspectives are focused on identifying common composting biomarkers, on investigating the causality process between chronic bioaerosol exposure and disease onset, and finally, on defining common exposure limits.

Bioaerosol exposure linked to the bioenergy production from waste and its effects on human health in occupational and residential environments has rising interest nowadays. The health risk associated with the exposure includes mainly infective diseases, allergies, chronic bronchitis, and obstructive pulmonary disease. A risk assessment’s critical point is the bioaerosol quality and quantity characterization. The aim of this study is to evaluate the application of different methods for the analysis of bioaerosol sampled in bioenergy plants. This study involved six Italian plants for the treatment of biomasses and energy production. Bioaerosol cultural evaluation was performed, by Surface Air System (SAS) sampler, and DNA was extracted from PM0.49 samples and Low Melting Agar plates. qRT-PCR followed by Denaturing Gradient Gel Electrophoresis (DGGE) and band sequencings were performed. The cultural method is able to detect less than 15% of what is evaluable with bio-molecular methods. A low sample alfa-diversity and a high beta-biodiversity in relation to feedstock and process were observed. Sequencing showed microorganisms with a hygienic-sanitary relevance such as Arcobacter, Pseudomonas, Enterobacter, Klebsiella, Enterococcus and Bacillus. Integrated cultural and biomolecular methods can be more exhaustive to evaluate bioaerosol’s exposure in the occupational environment.

Bioaerosols lead to human health diseases and composting plants are one of the main sources among human activities. In this study, a survey was conducted on such plants to evaluate bioaerosol risk management. A questionnaire was used to collect information on plant location, process types, collective and personal protective equipment, bioaerosol and particulate matter monitoring data, and occupational surveillance. We examined the data produced by 11 plants located in Italy. Self-control bioaerosol monitoring showed a global contamination index mean of 9908 CFU/m³ underlining a higher concentration (a) in plants with only aerobic process (CPs) with respect to plants that also combined anaerobic treatment of the waste (ADCPs) (p < 0.05) and (b) in facilities with biocells with respect to windrows (p < 0.01). Workers are generally more exposed when working without vehicles. Some areas such as pre-treatment and screening are more prone to higher bioaerosol concentrations, requiring more efficient collective protective equipment. Particulate matter monitoring showed concentration in line with occupational exposure limits for inhalable dust (1862 ± 1729 µg/m³) and breathable dust (276 ± 126 µg/m³), however, organic particle exposure risk assessment has to be carefully reviewed. Improvements in the training program, process design, and health surveillance are desirable as major preventive tools.

Purpose: The anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) is a treatment biologically optimizable. The analysis of the microbial balance within the digester allows not only to describe and improve the efficiency of the system but also to foresee potential variations after biochemical interventions. This work aims to highlight methanogenic population variations in two similar parallel digesters to identify bio-indicators for digestion performance after the inclusion of an additive. Methods: The analysed industrial case study involved the two parallel, pilot-scale, bio-digesters of ACEA Pinerolese Industriale. They had analogous design and fed by the same OFMSW except for an additive inclusion. The analyses by qRT-PCR, on both bio-digesters, have been performed to determine an impact of the additive on the growth and metabolic activity of total methanogens, Methanosarcina spp., Methanocorpuscolum spp., and Methanospirillus spp. Results: Collected data showed that the addition of biopolymers extracted from compost produced both total methanogens and Methanosarcina decrease (7.67 vs. 7.48 and 6.05 vs. 5.69 Log gene copies/mL sludge respectively, T-test p < 0.01) affecting slightly the methane yield (-8%). Methanosarcina was the highest expressed methanogen; however, the results suggested the involvement of a highly complex and heterogeneous methanogen community. Conclusions: Total methanogens and active Methanosarcina modulations are able to highlight major bio-methane production even if their shift is slight. Globally only 3–4% of the present and 12–13% of the active methanogens were described. However, biological approach can supply a proxy of production performance of the digester also concerning the feeding peculiarities. Graphical

Environmentally sustainable methods of waste disposal are a strategic priority. For organic waste management and innovative biological treatments present advantageous opportunities, although organic waste treatment also includes environmental drawbacks, such as bioaerosol production. This study aims to evaluate bioaerosol spread during an innovative experimental treatment. The process consists of two anaerobic steps: acidogenesis, which includes polyhydroxyalkanoate accumulation, followed by methanogenesis. Bioaerosol, PM10, and endotoxin concentrations were measured at three sampling points during different campaigns to evaluate: (1) the background levels, (2) the contamination produced in the pre-treatment stage, and (3) the residual contamination of the outgoing digested sludge. Environmental PM10 seemed to be generally quite contained, while the endotoxin determination was close to 90 EU/m³. Significant microbial concentrations were detected during the loading of the organic fraction of municipal solid waste (fungi > 1300 CFU/m³, Bacillus genus (≈10³ CFU/m³), higher Clostridium spp. and opportunistic human pathogens such as Pseudomonas aeruginosa and Klebsiella pneumoniae), suggesting a significant contamination level. Such results are useful for hazard identification in the risk assessment of innovative processes, as they reveal contaminants potentially harmful to both workers’ health and the environment.